147959-19-1 (S)-tert-Butyl 2,2-dimethyl-4-(2-oxoethyl)oxazolidine-3-carboxylate 10586317, aoxazolidine compound, is more and more widely used in various.
With the rapid development and complex challenges of chemical substances, new drug synthesis pathways are usually the most effective.147959-19-1,(S)-tert-Butyl 2,2-dimethyl-4-(2-oxoethyl)oxazolidine-3-carboxylate,as a common compound, the synthetic route is as follows.
ith key building block 6 in hand, its nitroaldol (Henry) reaction with nitromethane was examined (Table 1). LiAlH418- TBAF19- as well as t-BuOK20-catalyzed Henry reactions led to nitro alcohols 12 and 13 with low diastereoselectivity, reflecting that the existing stereogenic center is too far away from the newly created one to exert appreciable asymmetric induction (Table 1, entries 1-3).21 An obvious way of resolving this problem was the introduction of additional chiral information, i.e. application of a chiral catalyst. In fact double stereodifferentiation using Shibasaki’s well established heterobimetallic (,S)-BINOL catalyst 1422 (5 mol%, THF, -40 C, 3 d) led to 12 with high diastereoselectivity albeit in low yield (Table 1, entry 4).Recently, other highly efficient chiral catalysts for asymmetric Henry reactions have been developed. Thus, Corey23 and Maruoka24 have utilized chiral quaternary ammonium fluorides as catalysts while Trost25 has presented a dinuclear zinc catalyst. Salen-cobalt(II) complexes have been used by Yamada whereas J¡ãrgensen and Evans have introduced bis(oxazoline)-coprhoer(II) complexes. The latter seemed to be the catalysts of choice, at least for aliphatic aldehydes, with respect to attainable yields and degree of stereoselectivity. EPO Table 1. Diastereoselective Henry Reaction of Aldehyde 6 with Nitromethaneyield ratio0 entry catalyst conditions(%)a 12:131 LiAlH4 THF, rt 53 56:442 TBAF THF, rt 33 43:573 r-BuOK t- 72 23:77BuOH/THF,00C4 14 THF, -40 C 45 98:25 {Cu[(+> EtOH, rt 87 92:815]} (OAc)26 (CuK-)- EtOH, rt 85 9:9115]}(OAc)27 {Cu[(+> EtOH, rt 94 97:316]}(OAc)28 (Cu[(-)- EtOH, rt 91 8:9216I)(OAc)2a isolated yield b determined by HPLC analysis of crude reaction mixtures EPO Indeed application of Evans’ bis(oxazoline) copper(II) acetate-based catalysts {Cu[(+)- 15]}(OAc)2 and in particular {Cu[(+)-16]}(OAc)2 (5 mol%, EtOH, rt, 5 d) gave the desired nitro alcohol 12 both with high diastereoselectivity and in high yield (Table 1 , entries 5 and 7). Finally, to obtain selectively diastereomer 13, aldehyde 6 was reacted with nitromethane in the presence of the enantiomeric catalysts {Cu[(-)-15]}(OAc)2 and {Cu[(-)-16]} (OAc)2 respectively. In these cases slightly lower stereoselectivities and yields were observed reflecting a mismatched pairing (Table 1, entries 6 and 8).; Nitroaldol adduct 13 was prepared from aldehyde 6 (243 mg, 1.0 mmol) and nitromethane (0.55 mL, 10.0 mmol) in the presence of indabox ligand (-)-16 (19.7 mg, 0.055 mmol) and Cu(OAc)2-H2O (10.0 mg, 0.05 mmol) as described for diastereomer 12. The diastereomeric ratio 13:12 was determined by HPLC analysis (n-heptane//-PrOH 99:1; LiChrospher 250×4, Si 60, 5 mum; 1.5 mL/min; 215 nm; 13: t,- = 33.8 min; 12: tr = 42.4 min) of the crude reaction mixture to be 92 : 8. The crude product was purified by flash chromatography on silica gel (/j-hexane:EtOAc 3:1) to give 13 (211 mg, 91%) as a 92:8 mixture of diastereomers. For analytical purposes a small quantity of the diastereomers was separated by preparative HPLC (/iota-heptane/-PrOH 99:1; Hibar 250×25, Si 60, 5 mum, 15 mL/min; 215 nm) to afford 13 as a colorless solid: mp 58-60 0C; [alpha]22D -31.6 (c 1.08, CH2Cl2); IR (KBr): 3408 cm”1, 1661, 1554, 1407; 1H NMR (500 MHz, CDCl3): delta 1.50 (s, 9 H), 1.51 (s, 3 H)5 1.56 (s, 3 H), 1.57-1.64 (m, 1 H), 1.77 (ddd, J= 2.0, 11.3, 13.4 Hz, 1 H), 3.67 (d, J- 8.9 Hz, 1 H), 4.03 (dd, J= 5.5, 8.9 Hz, 1 H), 4.22-4.31 (m, 2 H), 4.33 (dd, J= 4.0, 12.4 Hz, 1 H), 4.46 (dd, J= 8.6, 12.4 Hz, 1 H), 5.13 (bd, J= 3.8 Hz, 1 H); 13C NMR (125 MHz, CDCl3): delta 24.3 (CH3), 28.0 (CH3), 28.3 (CH3), 39.9 (CH2), 53.7 (CH), 65.5 (CH), 68.1 (CH2), 80.1 (CH2), 81.8 (C), 94.1 (C), 154.5 (C); MS (CI) m/z (rel. intensity): 305 (2) [M+H]+, 188 (100); Anal. Calcd for Ci3H24N2O6: C, 51.31; H, 7.95; N, 9.20. Found: C, 51.39; H, 7.94; N, 9.14.
147959-19-1 (S)-tert-Butyl 2,2-dimethyl-4-(2-oxoethyl)oxazolidine-3-carboxylate 10586317, aoxazolidine compound, is more and more widely used in various.
Reference£º
Patent; LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN; WO2006/94770; (2006); A2;,
Oxazolidine – Wikipedia
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